SUMMARY Coccidioidomycosis, also known as valley fever, is caused by inhalation of fungal spores from species in the genus Coccidioides, which is primarily endemic in the desert soils of the Southwest U.S. The disease results in serious morbidity in thousands of people each year, millions of excess dollars in healthcare costs and significant days lost in schools and the workplace. While the public health and healthcare communities clearly understand the epidemiology and natural history of disease in humans, and the research community has made great strides in understanding the natural ecology of the pathogen in the soil, very little is understood about the presence of Coccidioides in ambient air, where exposure occurs. Environmental influences (e.g., weather, landscape, and air quality) affecting the presence and movement of the Coccidioides bioaerosol are therefore critical factors missing in the collective understanding of this disease. Without this understanding, hypothetical drivers of increased coccidioidal disease have commonly included severe weather events, such as Haboob dust storms, climate change in general, and human activities such as new development building, farming and outdoor recreation. This study aims to fill this current gap in knowledge about the Coccidioides interaction space, between soil and the host. The proposed research strategy includes a multivariate analysis of the spatial and temporal environmental factors associated with the presence and abundance of the Coccidioides bioaerosol in the ambient air across an endemic urban/suburban hotspot for disease (Specific Aim 1); and an analysis of the importance of Coccidioides strain diversity and overall mycobiome diversity (i.e., the whole fungal community) within the endemic airspace (Specific Aim 2). This work will be accomplished through the genomic analysis of Coccidioides and other fungi on daily high-volume air samples collected over two years across the Phoenix metropolitan region, where the majority of all coccidioidomycosis cases occur, in combination with the collection of environmental data (i.e., temperature, humidity, wind, and particulate matter) and human and canine epidemiological data. The analysis team for this One Health project includes expertise in mycology, genomics, human and animal epidemiology, environmental monitoring and meteorological modeling. This novel approach will: 1) reveal factors contributing to Coccidioides bioaerosol distribution and timing, and thus potentially to disease risk; 2) explore the relationship between disease and suspected weather event drivers of exposure; 3) provide a more robust understanding of the overall ecology of the pathogen; and 4) identify risk factors to build predictive models to inform the public, alert clinicians and direct public health risk mitigation.